Weakening of Western Disturbances in Response to Polar Sea Ice Melt in Climate Model Simulations

ABSTRACT The response of low‐latitude weather and climate to polar sea ice melt is not well understood. In this study, we run a suite of coupled and uncoupled simulations using the Community Earth System Model to investigate the effects of polar sea ice melt on western disturbance (WD) activity over the Indian subcontinent. In the coupled model simulation, the albedo of the sea ice is reduced in such a way that the increased absorption of the solar radiation would melt the sea ice. Further, the monthly climatology of sea surface temperature (SST) and sea ice concentrations (SIC) from the coupled model runs are used to force the community atmospheric model (CAM5) at higher resolution (50 km). WD vortices in the CAM5 simulations are tracked using an objective feature‐based tracking algorithm. Our analyses reveal that WD activity is reduced in the CAM5 simulations forced with the SST and SIC from the sea ice melt experiment. The reduction in WD activity is attributed to the subtropical jet becoming more baroclinically stable and undergoing an equatorward shift in response to the polar sea ice melt. The weakening and widening of the subtropical jet are consistent with the predicted changes to thermal wind and upper‐tropospheric meridional temperature gradient in response to the polar sea ice melt.